The present invention relates to a recoil starter which is adapted for use in an internal combustion engine, and in particular, to a recoil starter provided with a buffering/power-accumulating means which is interposed between a driving member comprising a rope reel which is designed to be rotated by the pulling of a recoil rope, and a driven member to which the torque of the driving member is transmitted.
A conventional recoil starter which is designed to be mounted on an internal combustion engine is generally provided with a driving member comprising a rope reel around which a recoil rope is wound, and a driven (idler) member comprising a centrifugal ratchet mechanism. When the internal combustion engine is desired to be started, the recoil rope (recoil handle) is pulled to revolve the rope reel, the resultant revolution of the rope reel being then transmitted, via the driven member, to a crankshaft of the internal combustion engine to thereby start the internal combustion engine.
As set forth in Japanese Patent Application No. H11-238642, the present inventors have previously proposed a modification of the aforementioned recoil starter, wherein a spiral spring mechanism is interposed, as the buffering/power-accumulating means, between the driving member and the driven member.
According to this modified recoil starter, since the spiral spring mechanism is interposed, as the buffering/power-accumulating means, between the driving member and the driven member, it is possible to derive a buffering effect from the spiral spring mechanism during the first-half driving process (until the piston of the internal combustion engine reaches to the top dead center thereof) in the pulling operation of the recoil rope (recoiling operation), and at the same time, to enable the pulling force of the recoil rope to be accumulated in the spiral spring mechanism. During the latter-half driving process, the pulling force thus accumulated in the spiral spring mechanism during the first-half driving process is permitted to be combined with the pulling force to be actually effected in the latter-half pulling operation of the recoil rope to thereby generate a resultant force, which is utilized as a force for starting the internal combustion engine.
As a result, it is possible to minimize a fluctuation in pulling force of rope so as to smooth the rope-pulling operation, thus enabling even a person having a weak physical strength to easily start the internal combustion engine.
However, this modified recoil starter previously proposed by the present inventors is accompanied with the following possible problems.
Namely, since this modified recoil starter is designed such that the spiral spring of the spiral spring mechanism is rewound so as to accumulate the pulling force during the first-half driving process in the pulling operation of the recoil rope (recoiling operation), that during the latter-half driving process, the pulling force thus accumulated during the first-half driving process is released, thus unwinding the spiral spring and enabling the spiral spring to be restored to the original released state thereof, while permitting the spiral spring mechanism to rotate in the direction to drive the crankshaft, and that after the start-up of the internal combustion engine, the interlocking engagement between the spiral spring mechanism and the internal combustion engine is permitted to be released due to the releasing action by the centrifugal ratchet mechanism attached to the driven member, thus rendering the spiral spring mechanism to become free, the spiral spring is permitted, due to the inertia of the releasing movement of the spiral spring, to be excessively kicked back in the unwinding direction (releasing direction) even after the spiral spring has taken the fully unwound and released state thereof.
Generally, a spiral spring is usually employed, as in the case of a watch, under the conditions where the spiral spring is completely wound up and is then incompletely unwound leaving one or two unreleased turns. In the case of the aforementioned recoil starter however, since the spiral spring mechanism is rendered free after the start-up of the internal combustion engine, the spiral spring is completely released without leaving even a single unreleased turn, and is still more permitted to be excessively kicked back in the unwinding direction. Namely, the spiral spring is not used in a manner which the spiral spring is inherently intended to.
Therefore, the innermost end region of the spiral spring is repeatedly and locally subjected to a winding/unwinding stress, thus giving rise to the generation of settling and bending at this innermost end region of the spiral spring. As a result, not only the durability of the spiral spring is badly affected, but also the internal hook end of the spiral spring which is fastened to the core portion of the actuating pulley of spiral spring mechanism tends to be disengaged from the core portion, thereby raising a possibility that the rope-pulling manipulation may result in a futile try.
The present invention has been made in view of the aforementioned problems, and therefore, it is an object of the present invention to provide a recoil starter having a spiral spring mechanism interposed, as a buffering/power-accumulating means, between a driving member comprising a rope reel which is designed to be rotated by the pulling of a recoil rope, and a driven member to which the torque of the driving member is transmitted, the recoil starter being characterized in that it is capable of inhibiting the generation of settling and bending in the spiral spring of the spiral spring mechanism, thereby making it possible not only to improve the durability of the spiral spring, but also to prevent the internal hook end of the spiral spring from being easily disengaged from the core portion of the actuating pulley of spiral spring mechanism. Another object of the present invention is to provide a spiral spring which is excellent in durability and therefore is suited for use in the recoil starter, etc.
With a view to attaining the aforementioned object, there is provided, in accordance with the present invention, a recoil starter which fundamentally comprises a driving member having a rope reel around which a recoil rope is wound to thereby enable the rope reel to be rotated by pulling the recoil rope, a driven (idler) member to which the torque of the driving member is transmitted, and a buffering/power-accumulating means interdisposed between the driving member and the driven member; wherein the buffering/power-accumulating means is enabled, during the driving process by the driving member, to accumulate the power supplied through the driving process while alleviating any impact to the driven member, the accumulated power being subsequently employed to drive the driven member, and wherein the spiral spring mechanism is rendered free after the start-up of an internal combustion engine.
In this case, the spiral spring mechanism is featured in that it comprises a spiral spring case placed close to the driving member, a actuating pulley placed close to the driven member, a spiral spring interposed between the spiral spring case and the actuating pulley, and means for rotating the spiral spring case only unidirectionally, wherein an outer end portion of the spiral spring and an inner end portion of the spiral spring are fastened to the spiral spring case and the actuating pulley, respectively.
In a preferable embodiment of the present invention, the spiral spring of the spiral spring mechanism comprises an outer circumferential wound portion where a predetermined number of turns of the outer circumferentially wound portion of the spiral spring are closely contacted with each other under a freely released condition of the spiral spring, and an inner circumferential wound portion which is constituted by at least one turn of the inner circumferentially wound portion of the spiral spring, wherein a clearance is provided between the outer circumferential wound portion and the inner circumferential wound portion. More preferably, the outer circumferential wound portion is constituted by a third turn and the following turns successive to the third turn, and the inner circumferential wound portion is constituted by a first turn and at least a portion of the second turn which is closely contacted with the first turn.
In another preferred embodiment of the present invention, the recoil starter is featured in that the actuating pulley is provided with a core portion around which the spiral spring is wound, that the spiral spring is provided, at an inner end portion thereof, with a C-shaped or ring-shaped internal hook end, that said core portion is provided with an inner end-holding portion into which the internal hook end is adapted to be inserted and held therein, that the spiral spring is provided, at an outer end portion thereof, with an external hook end, and that the spiral spring case is provided, at an outer circumferential wall thereof, with an outer end-holding portion with which the external hook end is adapted to be engaged.
Preferably, the inner end portion of the spiral spring is positioned, under a freely released condition of the spiral spring, at a position which is displaced from the location of the outer end portion of the spiral spring by a predetermined angle toward the direction which is opposite to the driving direction. Further, the rotational axial line of the spiral spring mechanism is preferably displaced from the proper center of the spiral spring by a predetermined distance toward the outer end portion of the spiral spring.
In a further preferable embodiment of the present invention, the outer diameter of the core portion of actuating pulley is made almost identical with the effective inner diameter of the first turn of the spiral spring. At the same time, the effective outer diameter of the spiral spring under the freely released condition thereof is made almost identical with the effective inner diameter of the spiral spring case. Further, the effective inner diameter of the first turn of the spiral spring and the effective outer diameter of the core portion are set to 25 mm or more (preferably, 30 mm or so).
In another preferred embodiment of the recoil starter of the present invention, the driving member is provided with a recoiling urging means for reversely revolving the rope reel so as to rewind the recoil rope, and also with a recoil ratchet mechanism for transmitting the torque of the rope reel to the spiral spring case.
The means for rotating the spiral spring case only unidirectionally is preferably constituted by a one-way clutch. Further, the driven member is preferably provided with an interlocking pulley having a power transmission mechanism through which the driven member is enabled to interlockingly coupled with the driving member. In this case, the power transmission mechanism may preferably be constituted by a centrifugal ratchet mechanism.
Meanwhile, the spiral spring according to the present invention comprises an outer circumferential wound portion where a predetermined number of turns of the outer circumferentially wound portion of the spiral spring are closely contacted with each other under a freely released condition of the spiral spring, and an inner circumferential wound portion which is constituted by at least one turn of the inner circumferentially wound portion of the spiral spring, wherein a clearance is provided between the outer circumferential wound portion and the inner circumferential wound portion.
More preferably, the outer circumferential wound portion is constituted by a third turn and the following turns successive to the third turn, and the inner circumferential wound portion is constituted by a first turn and at least a portion of the second turn which is closely contacted with the first turn. More preferably, the inner end portion of the spiral spring is positioned, under a freely released condition of the spiral spring, at a position which is displaced from the location of the outer end portion of the spiral spring by a predetermined angle toward the direction which is opposite to the driving direction.
More preferably, the effective inner diameter of the first turn of the spiral spring is set to 25 mm or more. The spiral spring according to the present invention may preferably be formed of a stainless steel sheet having a thickness of 0.5 to 0.7 mm. It is also preferable that an annealing treatment is performed on the inner circumferential wound portion of the spiral spring.
In the embodiment of the recoil starter where the spiral spring of the present invention which is constructed as mentioned above is employed, since at least a portion of the second turn is closely contacted with the first turn at the inner circumferentially wound portion of the spiral spring, even if the interlocking between the spiral spring mechanism and the engine is disengaged from each other after the start-up of the engine due to the free releasing effects to be obtained from the centrifugal ratchet mechanism mounted on the driven member, thereby rendering the spiral spring mechanism into a free state, and hence permitting the spiral spring to be excessively kicked back in the unwinding direction (releasing direction) thereof beyond the predetermined full unwound state of the spiral spring due to the inertia on this occasion, this kick-back stress to be repeated by the effects of rewinding-releasing (unwinding) on this occasion can be received by the entire body of the inner circumferentially wound portion, thereby making it possible to suppress the generation of a concentration of the stress in the vicinity of the internal hook end of the spiral spring.
As a result, the generation of settling or breakage of the spiral spring can be prohibited, thereby making it possible to improve the durability of the spiral spring, and at the same time, the internal hook end of the spiral spring can be prevented from being easily disengaged from the core portion provided at the actuating pulley of the spiral spring mechanism, thereby further improving the reliability of the starter.